There are numerous types of advance mechanisms presently in use to advance perforated materials in a sequential and time controlled manner into and out of a path of light. Of primary importance in the advancement of the perforated materials, such as film strips, is that of providing for dependability and reliability of repeated intermittent and accurate advancement in respect to a given distance.
In projection reading devices it is also important that the film be advanced in synchronization with the presentation of light and in this respect it is also necessary to provide for simultaneous stroking of the film for advancement purposes and a scanning of the exposed portion of film for controlled exposure of the materials contained thereon.
The advance mechanism should be of low cost containing a minimum number of components and should be versatile in that it can be used with a variety of different types of perforated materials such film, paper tape, timing charts and the like. The above referenced application is successful in achieving these objectives and naturally there is always room for further modified systems which also are successful in achieving the desired objectives for the advance mechanism.